Magnetic fields & induction worksheet with answers

Free printable Magnetic fields & induction worksheet: 6 problems from easy to exam level, with an answer key. Print it or save it as a PDF.

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1.Easy

A straight wire 80 cm long carries 4 A at an angle of 30° to a uniform magnetic field of 0.8 T. Find the magnitude of the force F on the wire.

B = 0.8 TI = 4 AL = 80 cmθ = 30°

F = N

2.Easy

A proton moves at 2.5 × 10⁶ m/s at an angle of 45° to a uniform magnetic field of 0.1 T. Find the magnitude of the magnetic force F on it.

|q| = 1.602 × 10⁻¹⁹ Cv = 2.5 × 10⁶ m/sB = 0.1 Tθ = 45°

F = fN

3.Medium

An electron moving at 3 × 10⁶ m/s enters a uniform magnetic field at right angles and moves on a circle of radius 0.1706 cm. Find the magnetic flux density B.

m = 9.109 × 10⁻³¹ kg|q| = 1.602 × 10⁻¹⁹ Cv = 3 × 10⁶ m/sr = 0.1706 cm

B = mT

4.Medium

A metal rod 60 cm long slides at 5 m/s along two rails in a uniform field of 0.6 T into the page. The rails are joined by a resistor of 1 Ω; the rod and rails have negligible resistance. Find the power P dissipated in the resistor.

B = 0.6 TL = 60 cmv = 5 m/sR = 1 Ω

P = W

5.Hard

A long air-core solenoid has 100 turns, a length of 20 cm and a diameter of 4 cm. Find the energy W stored in its magnetic field when it carries 2.5 A.

N = 100l = 20 cm⌀ = 4 cmI = 2.5 Aμ₀ = 4π × 10⁻⁷ T·m/A

W = µJ

6.Hard

A long air-core solenoid has 100 turns, a length of 20 cm and a diameter of 3 cm. Find the energy W stored in its magnetic field when it carries 2.5 A.

N = 100l = 20 cm⌀ = 3 cmI = 2.5 Aμ₀ = 4π × 10⁻⁷ T·m/A

W = µJ

Answer key

1. F = 1.28 N
2. F = 28.32 fN
3. B = 9.999 mT
4. P = 3.24 W
5. W = 246.7 µJ
6. W = 138.8 µJ

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